Essential Science: 3D printed rocket parts now a reality

Houston
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A sign that 3D printing has matured sufficiently for products to be entrusted for use in one of the most risk adverse areas, additive manufacturing produced materials are to be used in spacecraft.

The news comes from NASA, where technologists have succeeded in tested an RS-25 rocket engine, that contains a large 3D printed component, for the very first time. This is a significant stepping stone towards entire rocket engines being produced through 3D printing.

Over the short-term, the success of the trial is a step towards lowering the costs associated with the engines set to power NASA’s new heavy-lift rocket: the Space Launch System.

The Space Launch System is a type of space shuttle heavy expendable launch vehicle, and it is part of NASA's deep space exploration plans such as the much discussed manned mission to Mars.

Most powerful rocket ever

The Space Launch System is to be the most powerful rocket ever built, possessing a total thrust greater than that of the Saturn V (used for the Moon missions). This is not the end of the development, however, for the vehicle is to be upgraded over time with more powerful versions.

The rocket currently consists of two five-segment Solid Rocket Boosters (RS-25 engines), capable of a total thrust of 32,000 kiloNewtons (to put this into context, one newton is the force needed to accelerate one kilogram of mass at the rate of one meter per second squared in direction of the applied force). These will be the largest solid-propellant motors ever flown.

One risk affecting the performance of any rocket engine, occurring during flight, is where a rocket can experience powerful up-and-down vibrations. These vibrations are a result of propellant in the feed lines. With the new development, the 3D printed part tested is a so-named Pogo accumulator, designed to function as a shock absorber to prevent such vibrations and to avoid destabilization of a rocket’s flight (the name derives from a child's Pogo stick).

Through the use of 3D printing more than 100 welds were eliminated with the Pogo accumulator. This not only made the production faster it lowered manufacturing costs by nearly 35 percent. Reducing welds is important for with each weld comes with it the need for inspections and possible rework, based on a standard manufacturing error rate.

Public-private partnership

For the development NASA worked with Aerojet Rocketdyne of Canoga Park, California, U.S. The trials with the 3D printed hardware passed the acceptance criteria for performance, reliability, and safety. This prompted Andy Hardin, of NASA's Marshall Space Flight Center in Huntsville, to tell Controlled Environments magazine: "As we build future RS-25s, NASA and our partners are taking advantage of innovative manufacturing techniques, including additive manufacturing, or 3D printing, to make the engines more affordable.”

The rocket expert added: “3D printing is revolutionizing manufacturing, and the pogo accumulator is the first of many components that can be built more quickly and less expensively."

The new parts are not only to be used with new engines; NASA's fleet of 16 heritage engines are to be modified with the new controllers. Going forwards main combustion chamber, nozzle, ducts, valves, electrical and running gear will each incorporate affordability improvements produced from 3D printers.